Note: Modifying /etc/security/limits.conf Should Not Be Required AnymoreBeginning with the Ubuntu package jack-audio-connection-kit-0.118+svn3796-1ubuntu2 editing of /etc/security/limits.conf should not be required. JACK will write the following during post-installation to /etc/security/limits.d/audio.conf:

Now, reboot the system and boot into your -rt kernel (should be default).

This kernel is the same as the standard kernel but with real-time support, so everything should be as normal and the kernel can be used even when the machine is not used for music production.

JACK

Note: You don't need to start JACK through Qjackctl in this step, it can be handled from within Ardour. But later on, when applications should be connected, it is needed - so we might as well get used to it right away.

What is JACK ?

When it comes to the audio hardware in Linux, the kernel and ALSA (Advanced Linux Sound Interface) take care of getting it to work.

But this stack is unable to provide a transport channel for different audio applications to "talk" to eachother (audio sequencer and drum machine, for example). To accomplish this and to optimize the sound processing to lower latency, the JACK system is used.

Note: The easiest setup is to have a secondary soundcard with which JACK will be used. If only one soundcard is present, JACK will take control over it and it won't be possible to play any "regular" audio while JACK is running. When starting JACK through QJackCtl, be sure no other process is using the soundcard.

Installation

To be able to configure and start the JACK daemon through a graphical interface, start up a terminal and install QJackCtl with this command:

sudo apt-get install qjackctl

This application will then be found through Applications -> Sound & Video -> Audio Production -> Jack Control.

Configuration

The configuration depends on the capabilities of the soundcard, but be sure to check the "Realtime" box and select the proper input and output devices.

Connections in JACK Patchbay

Using the JACK transport

Third step - Using filters

There is no obvious superior way of using filters at this point of Linux music production.

We to prioritize between having stable and well-integrated but graphically displeasing and hindering plugins (LADSPA) or emulated, mostly non-free, unstable and badly integrated but state-of-the-art plugins (VST).

LADSPA

LADSPA (Linux Audio Developer's Simple Plugin API) is a simple, stable and well-supported plugin API which works very well in applications like Ardour.